PST mod ideas

[GlassWalker]

I have a second (used) PST on its way to me, so before I get to the typical mods like replacing the objective, I was wondering if there was anything useful I can try with two PSTs first?

The thought occurs, could I extract the etalon from the 2nd one and add it to the 1st? Double stack on the cheap. I'm not 100% sure on the threads but could it screw in series with the existing one? But would the positioning in the optical train be thrown out enough to make this unworkable? I'm not sure how much tolerance I have to work with here...

[hunterknox]

Merlin66 tried it. I think he called it his LADS (large aperture dual stack) scope - I'm sure he'll be along soon to give you his thoughts but in the meantime have a little search around...

[keithatrochdale]

You may find this forum useful for asking questions too;

http://solarchat.natca.net/index.php/en/?func=listcat

[Merlin66]

Yes,

I tried that. The threads are M50 x 1 and you need a specific length to get the etalons as close as possible but the optics not touching. ( I have a sketch of the adaptor I made. let me know if you need the detail.)

It works...but....

I found it far too fiddly to tune and was disappointed with the results....

A better double stack arrangement was a SM60 (or larger!!) up front and a PST etalon at the back ie a Modded PST with a SM60 - the results were truly amazing.

Hope this helps.

[GlassWalker]

I was wondering, in a double stack, don't both have to be more or less set to the same spot to see anything? So I can imagine tuning wont be fun unless you can take one out at will to get it in the right ball park. Focus issues aside, do they have to be really close? As for the results, is it not able to give much more selectivity than a single stack then? I was concerned the small aperture of the PST would be limiting anyway.

Longer term, I will be going for a stage 1 mod anyway... but thought this might be fun to try in the short term.

[Merlin66]

Yes,

there is a fair degree of trial and error in the individual tuning...the tilt axis if the etalons also should be aligned (!!??) They have to be VERY close together (unless you remove the rear positive lens from the front etalon and the front negative lens from the rear etalon)

The potential is there to reduce the bandwidth by x0.707 ie a nominal PST etalon of 0.8 A would double stack to 0.57A......

There's a lot of great results published with 40mm aperture Ha scopes....